1. Field of the Invention
The present invention generally relates to an information recording method that records multi-level data in an information recording medium, such as an optical disk, and an information recording apparatus that records multi-level data in an information recording medium, such as an optical disk.
2. Description of the Related Art
According to a conventional method to improve error correction capability in the case of continuous data error (burst error) due to a crack, and the like on the optical disk (for example, Patent Reference 1),
a data sequence in the direction of an inner code correction of a product code (i.e., a lateral data sequence, and often called a row) is made longer,
an ECC block is divided into four product-code blocks, for example, and
data are interleaved between blocks in the direction of the inner code correction such that the burst error is distributed.
Further, in order to increase the capacity of the optical disk, another conventional method (for example, Non-Patent Reference 1) raises recording density by performing multi-level recording (octal code recording) that records 0 through 7, instead of binary code recording that records 0 and 1, wherein 11-bit binary data are converted into four symbols of multi-level (8-level) data.
[Patent Reference 1] JPA, 2001-67813
[Non-Patent Reference 1]
Akihiko Shimizu, et al., “Multi-level Recording on Phase-change Optical Discs”, Ricoh Technical Report No. 28, pp. 34-41.
[Problem(s) to be Solved by the Invention]
However, according to the conventional information recording method described above, 16 data frames are divided into four 172 B blocks, inner parity code (PI) and outer parity code (PO) are added to each block and complicated interleaving is performed, which requires a greater scale of circuit.
Further, two 2 KB of user data blocks, ID (address information), and RSV (reserve: reserved space for future expansion and storing information such as user information, producer information, and copyright protection) constitute a data frame.
According to the present DVD, RSV is added every 2 KB of user data. It is desirable that data (contents) recorded in the present DVD can be recorded in an optical disk of the next generation in the same way as at present.
Assuming that the next generation optical disk is capable of storing, e.g., three times as much data as present, contents, such as movie software and computer software, stored in three DVD disks now, for example, can be stored in one disk. At this future time, it is desirable that no reworking be required. Specifically, it is necessary that RSV data can be attached every 2 KB.
According to the conventional technology, there is a problem that the present contents data cannot be recorded as they are, i.e., without reworking.
Next, according to the latter conventional information recording method described above, wherein recording density is raised, a modulation method when recording multi-level data and a demodulation method when reproducing the multi-level data are disclosed; however, a data structure of error correction is not disclosed, which hinders realizing a practical optical disk system.